Gas barrier films on which a thin film of a metal oxide such as aluminum oxide, magnesium oxide or silicon oxide is formed on a surface of a plastic substrate or a film have been widely used in packaging applications for articles that require blockage of various kinds of gases such as water vapor and oxygen, and packaging applications for preventing degeneration of foods, industrial products, pharmaceuticals and the like. The gas barrier film is used in liquid crystal display elements, solar cells, organic electroluminescence (EL) substrates, and the like, besides the packaging applications described above.
As a method for producing such a gas barrier film, principally a method of forming a gas barrier layer by a plasma chemical vapor deposition (CVD) method (chemical gas-phase growing method, chemical evaporation method), a method of applying a coating solution having a polysilazane as a main component, followed by carrying out a surface treatment, or a method using these methods in combination is known (see, for example, Patent Literatures 1 and 2).
An invention described in Patent Literature 1 discloses that an increase of thickness and suppression of cracks for high gas barrier properties are achieved by a laminate formation method of repeating steps of forming a polysilazane film having a thickness of 250 nm by a wet method and applying thereto vacuum ultraviolet light twice or more.
An invention described in Patent Literature 2 discloses a method for enhancing barrier properties by applying and laminating polysilazane onto a gas barrier layer formed on a resin base by a vacuum plasma CVD method, and reinforcing the gas barrier layer by a heat treatment.